APPLIED PHYSIOLOGY 



ton or linen, but when the temperature of the air is higher 

 than that of the body, it prevents the heat from entering, 

 and thus is cooler than linen or cotton. So men who tend 

 hot furnaces are cooler if they wear thick flannel than if 

 they wear linen or cotton. 



Silk is also a poor conductor of heat. While more ex- 

 pensive than wool, it is lighter in weight and feels softer 

 to the skin, and so makes the best kind of clothing. 



Fur is the poorest conductor of all, and is the best pro- 

 tector against cold. Nature has given a thick coat of fur 

 to animals that live in cold regions. In winter their fur 

 is long and thick, but it drops out during spring, and a 

 new fur grows during the summer, becoming thick and 

 long again by the following winter. 



Air itself is a poor conductor of heat, and when a considerable quan- 

 tity is imprisoned in the meshes of cloth, the garment offers a greater 

 resistance to the passage of heat. So loosely woven cloth is much 

 warmer than cloth made up of tightly twisted thread. Fur is warm 

 largely because of the amount of air which it imprisons. For the same 

 reason loose clothing is warmer than tight-fitting clothes. 



419. Color and heat. When exposed to the sun, black objects 

 take up twice as much heat as white objects. This difference of tem- 

 perature is noticeable in clothing. Light-colored or white clothing is 

 best for summer, and dark-colored or black for winter. 



420. Distribution of clothing. The different parts of the 

 body vary in their ability to resist cold. The face and hands usually 

 need no covering. The feet need less than the body, while the back, 

 chest, and abdomen need the most. Nature has distributed fur upon 

 the animal's body in the same way, leaving the head and feet poorly 

 covered. The sense of warmth is the best guide as to the amount of 

 clothing to be worn on any part. A person should wear enough to 

 keep each part of the body comfortably warm, while no part, especially 

 one which is usually left uncovered, should be covered so as to be 

 uncomfortably warm. 



Dampness produces cold by the evaporation of water. If all the 



